Forests and Drinking Water

Forests capture rainfall and replenish and cleanse our water supply. Although these ecological services provided by forests are widely accepted in the scientific community, they have not really been translated into the language that most often drives planning and land use decisions at the local level: dollars. Local government officials often make tough decisions about growth at the expense of natural resource conservation, and they must make these decisions without the benefit of economic data that measures the true costs of development and values of natural resources. 

For decades, technology has replaced, to some extent, the services provided by forests but at a high price.  Billions of dollars are invested in the construction and upgrade of water treatment plants to clean our public water supply that has been degraded by pollution as a result of industrialization and urban development. In fact, water utilities spend 19 times more on water treatment chemicals every year than the federal government invests in protecting lakes and rivers from pollution in the first place using techniques such as conservation of forest land (Frost & Sullivan 2004; Gross 2003; EPA 2009a; EPA 2009b; EPA 2009c; EPA 2009d).

The Forest Service estimates that nearly 1 million acres of forest were converted to developed uses each year in the 1990s, and by 2050, an additional 23 million acres of forests may be lost due to development (Stein et al., 2005). Areas experiencing the most forest loss are often suburban and urbanizing communities where municipal staff struggle to keep up with the growth and may not have adequate tools to manage it.  How does this loss of forest cover translate to costs incurred by communities for sustaining quality, long term water supply? The answer to this question is largely unknown as few communities track increases in drinking water treatment costs (or other community services) with the loss of forest land or evaluate these possible impacts prior to approving new developments.

Research is needed to identify the specific economic connections between forests and drinking water based on the available science. This research can be used to: a) put advance planning for water supply and forest conservation at the forefront of community issues, b) make the case for forest conservation to protect drinking water, c) encourage the use of incentives for forest conservation and tree planting that are more reflective of their true value, and d) factor in the costs of drinking water supply and treatment when evaluating development alternatives.

Several recent studies have addressed the topic of forests and drinking water:

  • A survey of 27 water suppliers was conducted in 2002 by the Trust for Public Land and the American Water Works Association.  They found that for every 10% increase in forest cover in the source watershed, treatment and chemical costs decreased by approximately 20%, up to about 60% forest cover (see figure below).  Not enough data were obtained on drinking water watersheds with more than 60% forest cover; however, the study authors suggest that treatment costs level off when forest cover is between 70 and 100 percent.  About 50-55% of the variation in treatment costs was explained by the amount of forest cover in the watershed.  The other 50% was attributed to the varying treatment practices used, the size of the treatment facility, and the characteristics of development and agricultural land in the watershed, including use of best management practices (BMPs).


Relationship between watershed forest cover and drinking water treatment cost (Ernst, 2004)

  • A second study conducted by the Trust for Public Land (Freeman et al., 2008) summarized raw water quality data, forest cover data, and drinking water treatment cost data for 60 water treatment plants across the country. This study found that there were significant relationships among percent land cover, source water quality, and drinking water treatment costs.  Decreased forest cover was significantly related to decreased water quality, while low water quality was related to higher treatment cost. The variability associated with the potential treatment costs given a change in watershed land cover precluded the development of a statistical model to predict treatment costs with certainty.
  • The importance of forest protected areas to drinking water is discussed in Running Pure, a research report by the World Bank / WWF Alliance for Forest Conservation and Sustainable Use.  Research found that approximately 1/3 of the world's 105 largest cities obtain a significant portion of their drinking water from protected areas and that well managed natural forests provide benefits to urban populations in terms of high quality drinking water.
  • The Forest-to-Faucet Partnership is a joint venture of the University of Massachusetts Amherst and the USFS Northeastern Area Watershed Program that aims to enhance the awareness, understanding and management of forests and water.  A project of this partnership, called Forests, Water and People, examines drinking water supply and forest lands in the Northeast, Midwest, and Southern regions of the United States.  The analysis uses maps produced in a geographic information system (GIS) to highlight the connection between forests and the protection of surface drinking water supplies, also known as the "forest to faucet" connection.   The analysis ranks watershed based on their ability to produce clean water, and identifies those watersheds located in areas important for surface drinking water supply, are privately owned, and are in need of protection from development pressure.  Reports and data from this project are available for download here.
  • The American Forest Foundation, along with key partners, is developing and implementing a Northern Forest Watershed project that will financially recognize the value of forested watersheds to municipal and other downstream users. The project will provide economic incentives and technical assistance for family woodland owners to restore, enhance, and protect aquatic resources in two critical watersheds in the Northern Forest region—the Crooked River in Maine and the upper Connecticut River in New Hampshire and Vermont.
  • The U.S. Endowment for Forestry and Communities (the Endowment) is funding a “Healthy Watersheds through Healthy Forests Initiative.” The multi-million dollar initiative seeks to advance the connection between forest management and water quality and quantity. Partnering organizations include: Conservation Trust for North Carolina and partner land trusts, working in the Upper Neuse River Basin located in central North Carolina; Pinchot Institute for Conservation, working in the Upper Delaware River Basin located in Pennsylvania, New Jersey, and New York; and Virginia Department of Forestry, working in the South Fork Rivanna Reservoir Watershed located in Albemarle County, Virginia. “We are seeking to link urban water consumers with rural forestland owners to reinforce the connection between upstream environmental benefits of healthy forests with the needs of downstream water users,” said Endowment President Carlton Owen. “This project comes at a crucial time when people everywhere must begin to work more directly with their governments and water suppliers at all levels to meet growing water needs during extended periods of drought likely to be exacerbated by climate change,” Owen continued. Under the HWHF Initiative, at least $6 million will be invested in the three watersheds.

Forests and Drinking Water Resources

Barten, P.K., and C.E. Ernst., 2004. Land Conservation and Watershed Management for Source Protection. Journal of American Water Works Association 96(4):121135.

Barten, Paul K., Kathleen A. Blaha, Avril L. de la Crétaz, Caryn E. Ernst, Kathryn A. Lanouette, Marcus G. Phelps, Lizabeth Shay, Albert H. Todd, Yanli Zhang, and Matthew H. Zieper., 2003. Land conservation for source water protection: Mapping, assessment, and implementation. Proceedings of the International Congress on Watershed Management for Water Supply Systems, M.J. Pfeffer, D. van Abs, and K.N. Brooks (Editors), New York, NY, July 2003, American Water Resources Association.

Dearmont, D., McCarl, B. A., and D. A. Tolman. 1997. Costs of Water Treatment Due to Diminished Water Quality: A Case Study in Texas. Texas A&M University Department of Agricultural Economics. College Station, TX. 

Ernst, Caryn.  2004.  Protecting the Source. Land Conservation and the Future of America’s Drinking Water. The Trust for Public Land and the American Water Works Association. San Francisco, CA. 

Environmental Working Group. 2004. National Assessment of Tap Water QualityEWG assembled an unprecedented database of 20 million drinking water quality records provided by water utilities since 2004. It reveals a total of 315 contaminants found in tap water supplied to 256 million Americans in 48,000 communities in 45 states. Among the contaminants were 202 chemicals that are not subject to any government regulation or safety standards for drinking water.

Freeman, J., Madsen, R., and K. Hart. 2008. Statistical Analysis of Drinking Water Treatment Plant Costs, Source Water Quality, and Land Cover Characteristics. Trust for Public Land white paper.

Food and Agricultural Organization of the United Nations. 2008. Forests and Water This report discusses "red flag" forest situations such as cloud forests, vernal pools, avalanche protection forests, etc. and ecosystem services, among other topics.

Frost & Sullivan.  2004.  Market Competition Intensifies as Water Treatment Chemical Manufacturers Woo Small Client Base.  Business Wire.

Gross AC, Richardson MB.  2003.  Water treatment chemicals - Focus on Industries and Markets. Business Economics. 

Stein, S.M., McRoberts, R. E., Alig, R. J., Nelson, M. D., Theobald, D. M., Eley, M., Dechter, M., and M. Carr. 2005. Forests on the Edge. Housing Development on America’s Private Forests.  USDA Forest Service. Technical Report PNWGTR636. 

The National Academies.  2008.  Hydrologic Effects of a Changing Forest Landscape. The National Academies Press. Washington, DC.

U.S. Environmental Protection Agency (USEPA).  2009a.  Drinking Water State Revolving Fund (DWSRF).

U.S. Environmental Protection Agency (USEPA).  2009b.  Cumulative U.S. Drinking Water SRF Set-Aside for Local Assistance and Other State Programs.

U.S. Environmental Protection Agency (USEPA).  2009c.  Drinking Water SRF Set-Aside for Local Assistance and Other State Programs.

U.S. Environmental Protection Agency (USEPA).  2009d.  Clean Water State Revolving Fund National Information Management System Reports. Summary Reports (Fund Status & Project Assistance).

U.S. Environmental Protection Agency (USEPA). 2006. Growing Toward More Efficient Water Use: Linking Development, Infrastructure, and Drinking Water Policies. This document addresses the challenges of meeting the demand for safe drinking water under the pressure of growth.

10,000 Friends of Pennsylvania. 2007. Water and Growth. This report discusses the connection between water supply and land use in southeastern PA. 

US Forest Service. 2000. Water & the Forest Service. This publication focuses on the role of forests in water supply - including quantity, quality, timing of release, flood reductions and low flow augmentation, economic value of national forest lands, and economic benefits of tree cover for stormwater reduction in urban areas.

US Forest Service. 2010. Water, Climate Change and Forests. This publication focuses on watershed stewardship for a changing climate.